> ## Documentation Index
> Fetch the complete documentation index at: https://docs.flowpayroll.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Calculate gross to net values



## OpenAPI

````yaml /api-reference/specs/pay-api.yaml post /calculator/grosstonet
openapi: 3.0.3
info:
  title: FlowPayroll API
  description: >-
    API for payroll management, including payroll upload, lock, HMRC submission,
    employee management
  version: 0.1.0
servers:
  - url: https://api.sandbox.flowpayroll.ai/v1
security:
  - XAuthToken: []
    XOrgId: []
tags:
  - name: Employees
    description: >-
      Create, retrieve, update, and delete employee records, and look them up by
      NI number or payroll ID.
  - name: Starters & leavers
    description: Set and clear starter and leaver details, individually or in bulk.
  - name: Tax codes
    description: >-
      Manage employee tax codes and query the effective tax code and NI category
      on a given date.
  - name: NI & identifiers
    description: Manage NI categories, National Insurance numbers, and payroll IDs.
  - name: Student loans
    description: Start and end student and postgraduate loans.
  - name: Payroll setup
    description: Assign an employee's payroll config and set opening balances.
  - name: Payroll
  - name: Payroll lines
  - name: PayrollConfig
  - name: Pay Elements
  - name: Calculator
  - name: Payslip
  - name: RTI
  - name: YearEnd
  - name: Organisation
paths:
  /calculator/grosstonet:
    post:
      tags:
        - Calculator
      summary: Calculate gross to net values
      operationId: GrossToNetCalculator
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/GrossToNetDto'
      responses:
        '200':
          description: Calculation Complete
          content:
            application/json:
              schema:
                type: object
                allOf:
                  - $ref: '#/components/schemas/ResponseBody'
                  - properties:
                      content:
                        type: object
                        properties:
                          data:
                            $ref: '#/components/schemas/CalculationResult'
        '400':
          description: Invalid calculation data or unsupported formula
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ResponseBody'
components:
  schemas:
    GrossToNetDto:
      type: object
      properties:
        taxCode:
          type: string
          description: Tax code for the calculation
          example: 1257L
        gross:
          type: number
          description: Gross amount to calculate from
        studentLoanPlan:
          type: string
          description: Student loan plan type
          enum:
            - Plan1
            - Plan2
            - Plan4
            - Plan5
        postGradLoanPlan:
          type: boolean
          description: Indicates if the employee has a postgraduate loan plan
        calculationName:
          type: string
          description: Name of the calculation formula to use
          enum:
            - '2024'
            - '2025'
        grossToDate:
          type: number
          description: Gross amount to date
        period:
          type: integer
          description: Period for the calculation
        payFrequency:
          type: string
          description: Unit of the period
          enum:
            - Weekly
            - Fortnightly
            - FourWeekly
            - Monthly
            - Quarterly
            - Annual
        week1Month1:
          type: boolean
          description: Indicates if the calculation is for Week 1/Month 1
        niCategory:
          type: string
          description: National Insurance category
          example: A
        taxToDate:
          type: number
          description: Tax amount to date
          example: 1000
      required:
        - taxCode
        - gross
        - calculationName
        - period
        - payFrequency
        - niCategory
    ResponseBody:
      type: object
      properties:
        message:
          $ref: '#/components/schemas/MessageWithTokenResponse'
        content:
          type: object
          properties:
            data:
              type: object
              nullable: true
            metadata:
              type: object
              nullable: true
              properties:
                dateFormat:
                  type: string
                  default: yyyy-MM-dd
                dateTimeFormat:
                  type: string
                  default: yyyy-MM-ddTHH:mm:ss.fffZ
                paginationToken:
                  type: string
                  nullable: true
        validationIssues:
          type: array
          items:
            $ref: '#/components/schemas/ValidationIssue'
        messageToken:
          type: string
    CalculationResult:
      type: object
      properties:
        taxForPeriod:
          type: number
          format: decimal
          description: Tax calculated for this period
        employeeNi:
          type: number
          format: decimal
          description: Employee National Insurance contribution
        employerNi:
          type: number
          format: decimal
          description: Employer National Insurance contribution
        studentLoan:
          type: number
          format: decimal
          description: Student loan deduction
        postGradLoan:
          type: number
          format: decimal
          description: Postgraduate loan deduction
        netPay:
          type: number
          format: decimal
          description: Net pay after all deductions
    MessageWithTokenResponse:
      type: object
      properties:
        text:
          type: string
        token:
          type: string
        tokenArguments:
          type: array
          items:
            $ref: '#/components/schemas/ValidationIssueArgument'
    ValidationIssue:
      type: object
      description: >
        Field validation item. `reasonToken` is a stable snake_case key for i18n
        or custom client messages; `reason` is the default English text from the
        API.
      properties:
        field:
          type: string
          description: Dot-path of the field (e.g. name.firstName, address.line1).
        reason:
          type: string
          description: Default human-readable message.
        reasonToken:
          type: string
          description: Machine-readable error identifier (snake_case).
        reasonTokenArguments:
          type: array
          nullable: true
          items:
            $ref: '#/components/schemas/ValidationIssueArgument'
    ValidationIssueArgument:
      type: object
      properties:
        name:
          type: string
        value:
          type: string
  securitySchemes:
    XAuthToken:
      type: apiKey
      in: header
      name: X-Auth-Token
      description: Access token obtained from OAuth2 client credentials flow
    XOrgId:
      type: apiKey
      in: header
      name: X-Org-Id
      description: >-
        Organisation to scope the request to. Required when the principal can
        access more than one organisation; optional for single-organisation
        principals (the authorizer resolves it automatically).

````